You may be able to spray the cleaner into the throttle body with the engine running if you leave the sensors connected that are in the intake hose going into the throttle body. Doing so will clean things up somewhat including some of the intake deeper in, but it won't be enough to properly clean the throttle body.
Some do remove the throttle body to clean it, but it usually isn't necessary.
My method is to shut the engine off, remove the intake tube from the throttle body (I find it easiest to remove it completely, from the air filter to the thorttle body), hold the throttle wide open (with the help of an assistant inside the car), spray the cleaner into the opening and let it start working on the entire bore of the throttle body and from the opening to well behind the throttle plate, also both sides of the throttle plate, with a small soft brush (an acid brush from a hardware store is ideal, you know the type, looks like a large art brush with a metal handle about 6" long) brush the bore and the throttle plate. Use a soft rag as well and gently polish the bore and the throttle plate, wiping out the excess cleaner. Make a special effort to clean the black carbon ring in the bore just behind the throttle plate, as this is what causes most of the disruption in air flow. You won't need to use the whole can. I can usually do several cleanings with one can.
Be careful of the teflon coating on the bore of the throttle body. It was intended to make it unnecessary to clean the throttle body. It helps to cut down on build up, but it doesn't prevent it. Don't scrape or scrub too hard so that the teflon continues to do what it can to minimize future build up, but don't be afraid to clean it even though there is a sticker on the throttle body telling you not to.
Put things back together and start the engine. The engine will be hard to start from all the junk left behind. You may need to hold the throttle wide open while cranking to clear it out. (Holding the throttle wide open shuts off the injectors.)
After starting the engine and allowing things to stabilize there are a few other things you may want to consider doing at the same time. Clean the PCV valve. It is right next to the throttle body. Make sure the air filter is in good shape, replace it if in doubt. You may want to clean the idle air control valve, especially it there have been signs that it has been sticking. I usually also add a bottle of injector cleaner to the tank (my preference if Techron or Red Line). You may need to reset the adaptive strategy if the throttle body was really dirty. If you are planning on changing oil or spark plugs, do it after cleaning the throttle body as you will add some trash to the oil and may lightly foul the spark plugs (although neither of these is usually enough of a problem to worry about).
Enjoy yourself. You will be surprised at how much better the engine runs after cleaning the throttle body. I always am.
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